The present invention relates to an imaging optical system, and an imaging apparatus having the imaging optical system.
Recently, digital cameras, digital video cameras and digital electronic devices in which an imaging module is mounted, such as a mobile phone, a PDA (Personal Digital Assistant), a PND (Portable Navigation Device), a PHS (Personal Handy phone System), a portable game machine and a notebook computer, have become widespread. Such cameras and digital electronic devices include a device in which an imaging optical system (a so-called bending optical system) configured to have an optical path elongated in a direction orthogonal to a direction of thickness of a device body is mounted so as to decrease the thickness of the device body. Hereafter, for convenience of explanation, the direction of thickness of a device body is referred to as “a case thickness direction”, and the direction orthogonal to the case thickness direction is referred to as “a case surface direction”.
Incidentally, when an optical path is directed to the case surface direction, a sensor surface of an image pickup chip needs to be positioned to be parallel with the case thickness direction so that an object image can be incident on the sensor surface of the image pickup chip. However, since an outer dimension of the image pickup chip in the sensor surface direction is large, it becomes difficult to design a device body case to be thin when the sensor surface is positioned to be parallel with the case thickness direction.
Each of Japanese Patent Provisional Publications No. 2006-058840A, No. 2006-154702A, No. 2007-033819A, No. 2004-247887A, No. 2007-316528A and No. 2008-268700A discloses an imaging optical system configured to decrease the dimension in the case thickness direction by positioning a sensor surface of an image pickup chip to be parallel with the case surface direction. Specifically, in the imaging optical system disclosed in these publications, a prism is arranged immediately before the image pickup chip and an optical path is bent to the case thickness direction.